DESCRIPTION (adapted from the Abstract): In the search for a means to modify adolescent sexual behavior, advocates of many HIV prevention interventions have appealed to what are for adolescents relatively weak motivations: those related to health and bodily harm. Social motivations are likely to be far stronger determinants of sexual behavior, yet these frequently have been viewed as obstacles rather than as variables that might be manipulated directly to prevent HIV infection. In the first four years of the proposed study, the Principal Investigator will examine the manner in which the social environment affects cognition and behavior related to sex of African American and White youth, aged 11 to 15 years. The focus will be on what has to date been understudied in this field: face-to-face interaction within cliques in a school environment and the role of communication and language in determining peer behavior. The primary specific aim of the project is to develop an empirically-based model of the social mechanism of peer influence related to sex of African American and White adolescents as it changes over the period from early to middle adolescence. The Investigator will conduct an ethnographic study of a cohort of 24 male and 24 female African American and White adolescents over a 4-year period as they move from the sixth through the ninth grade. His primary study methods will be ethnographic observation of cliques and audiotape recordings of clique social interaction supplemented by experience-focused interviews with a subset of clique members. Specifically, the Investigator will study adolescent peer culture at four levels: the crowd, the clique, the friendship clique or dyad and the romantic/sexual relationship. He will: conduct ethnographic observations in a range of venues where cliques congregate and interact; record and analyze field notes concurrent with data collection using methods of grounded theory; interview one in four clique members regarding their experience of clique membership as well as regarding gender and sexuality, analyzing also, the transcripts of interviews and of recorded interaction with grounded theory methods. Throughout the first four years and during the summers following each year of observation, primary effort will be devoted to model building. The transitions from junior high school to high school will be studied closely to determine variables affects change in peer influence structures. The goal of the study will be to understand the mechanism of adolescent peer influence sufficiently to be able to experiment with behavior change vehicles and test implementation of one pre-intervention based on social context methods in the fifth year of the study.